The present invention relates to a method for determining a closed trajectory curve by means of a laser and a laser light sensor having a flat field of view as well as an apparatus for determining a closed trajectory curve.
Methods and apparatuses of the kind mentioned in the introduction are used, in particular, for apparatuses and methods by means of which any existing misalignment of two shafts that are connected to each other by a coupling can be determined. Such misalignments, that is, deviations from the situation in which the axes of rotation or central axes of shafts that are connected to each other via the coupling are aligned, often lead to undesired vibrations during operation of the apparatus having the two shafts.
Methods and apparatuses for determining misalignment are known, for example, from DE 195 06 471 A1, DE 102 36 555 A1, DE 101 42 462 A1, DE 101 38 831 A1, and DE 39 11 307 A1.
Generally known from DE 199 49 834 A1 is a method for determining the alignment of a cylindrical body with respect to a reference direction.
The use of an angle sensor in the automobile branch for determining a direction of travel is known from DE 10 2004 024 398 A1 and the use of a magnetic sensor for determining the linear position of a movable element is known from DE 11 2004 000 113 T5.
It is known from DE 102 36 555 A1, for example, how to use at least one flat field of view of a laser light sensor together with a laser for determining the misalignment of two shafts that are connected to each other via a coupling on the basis of elliptical trajectory that is traced on the at least one flat field of view by the laser light spot of the laser light beam and is described on the field of view during rotation of the first or second shaft when the laser or the field of view is linked to at least one of the two shafts in a rotationally fixed manner and the laser beam is directed onto the field of view.
In order to determine any existing misalignment from the determined trajectory curve, which generally takes the shape of an elliptical trajectory, not only the X coordinates and Y coordinates of the laser light spot are recorded, but, in addition, also the angle of rotation of the first or second shaft relative to a reference angle value or a predetermined angular position of the first or second shaft. For measurement of the angle of rotation determined from the angular position or the reference value, resort is generally had to an angle measurement instrument, such as an inclinometer, which enables the measurement of any inclination relative to the direction of gravitational force.
The measurement of the angle of rotation for determination of the angular position of the respective ellipse described by the laser light spot functions with high accuracy when shafts of machines that are essentially horizontally aligned are to be aligned. For the determination of any existing misalignment of essentially vertically aligned shafts, an inclinometer cannot be used or cannot be used with sufficient accuracy owing to the principle of measurement. This is correspondingly also the case for unstable floors, that is, when shafts that are to be aligned are situated on a ship.